Pegatron Chief Financial Officer Charles Lin said: "The factory has not started operations yet. Part of the facility is still under pre-operation inspection and part is running trial production."

Apple has said that it is investigating the incident.

"Our hearts go out to the people who were hurt in Songjiang. We are working closely with Pegatron to understand the cause of this accident," spokeswoman Carolyn Wu said, according to Appleinsider.

Ri-Teng was reportedly expanding the factory to compete with rivals including Foxconn, whose 400,000-plus employee facilities are also used by Apple and other companies to cheaply produce their electronics for sale overseas.

Several other high-profile explosions, fires and controversies have hit factories used to produce Apple products and other electronics. In May 2011 three employees were killed and 16 were injured in a dust explosion at a Foxconn factory in Chengdu, China, which is used to produce iPad 2 parts.